For centuries, people have harnessed the wind's energy for power, to sail ships (the ancient Egyptians) or to power windmills to grind grain (the Persians). The Dutch are famous for their windmills, which have formed the basis for the design of the modern wind turbines that we see today.

How does wind energy work?

Wind is caused by sunlight unevenly heating the surface of the Earth. During the day, air over the land heats up more quickly than air over the water, making it expand and rise. As it does so, cooler, more dense air rushes in beneath it, creating an air current. Some giant wind currents are driven by hot air at the equator and cool air at the poles. In Britain, we have enough wind to power the country several times over.

Turbines harness this energy by working like an old-fashioned windmill with rotor blades that face into the wind. When the blades are spinning, they drive a shaft that is connected to an electrical generator by a gearbox. Most wind turbines produce electricity when the wind is blowing at 10-30mph. One 1.8mW wind turbine produces enough electricity for 1,000 households every year.

What are wind farms?

Turbines tend to be built together, as "windfarms", to produce more electricity in places that have strong, steady winds.

Windfarms can be onshore - on ridgelines, at the tops of rounded hills, open plains and gaps in mountains; near shore - on land within 3km of a shoreline, or offshore - generally 10km or more from land.

Onshore windfarm projects are finding it increasingly difficult to get planning approval because opposition to them is becoming more entrenched and better organised.

Offshore farms cost more to build but produce more electricity because they usually stand in open, windier spots. However, current offshore farms can encroach on shipping lanes, affect seabird sanctuaries and disturb marine life, limiting the number of suitable sites.

Wind energy is now available for both large and small-scale electricity generation, with huge technological advances over the past 20 years.

How many windfarms are there in the UK?

The UK has some of the best wind resources in Europe, if not the world, in both onshore and offshore locations. This makes the British Isles a very attractive location for wind developments, as high average wind speeds and good reliability results in more power output and lower costs.

The number of windfarms in the UK is steadily increasing. The first windfarm was set up in November 1991. According to the British Wind Energy Association, there are currently 186 operational windfarm projects in the UK, with 2,120 turbines creating enough energy to power the equivalent of 1,523,052 homes and saving 6,156,175 tonnes of carbon.

However, wind turbines do not yet make a significant contribution to electricity production, making up less than 1% of the national total.

Wind is really a form of solar power, so it has similar benefits of being clean, abundant and free. Some estimates suggest there is enough wind to generate one-third of the world's electricity. Small wind turbines can be used in remote places to power homes that are too far away from the national grid.

What are the arguments against?

The major problem with wind power is that it is intermittent, so it can only be used to generate electricity when the wind is blowing strongly enough. Good sites for wind turbines are often quite remote, either offshore or up on mountainsides, far from the cities where the energy is most needed.

Another argument against large-scale windfarms is their impact on the natural landscape. Because they generally have to be positioned on hills to get the maximum benefits of the wind, some complain that they ruin the landscape.

Onshore windfarm projects are finding it increasingly difficult to get planning approval in the UK because local residents are fighting against windfarms being positioned in their area. There are now 151 UK anti windfarm action groups in the UK which have been formed as a result of windfarm developments planned for local countryside areas.

Another argument made against windfarms – particularly offshore ones- is the threat to birds. However, appropriately positioned windfarms do not pose a significant hazard for birds, says the RSPB.